Backside Dielectric Cap for Gate Sealing During Backside Processing
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Solution Overview
Problem
In semiconductor technology, the exposure of high-k dielectrics during backside processing poses a risk of threshold voltage shift due to hydroxyl group diffusion, and there is a risk of gate to direct backside source/drain contact shorts due to inadequate protection of the gate structure.
Innovation Solution
A self-aligned backside dielectric cap is formed during frontside processing, which seals the gate structure and prevents exposure during backside processing, thereby mitigating gate to direct backside source/drain contact shorts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the gate structure is left exposed during backside processing, then direct backside source/drain contacts can be formed, but gate to direct backside source/drain contact shorts occur and threshold voltage shifts due to hydroxyl group diffusion
Solution Approach 1:
A backside dielectric cap is formed during frontside processing before the wafer is flipped for backside processing. This preliminary action protects the gate structure in advance, preventing contact shorts and threshold voltage shifts during backside processing without requiring additional protection steps after flipping.
Solution Approach 2:
The backside dielectric cap acts as an intermediary protective layer between the gate structure and the backside source/drain contact structures. It physically separates these components during backside processing, preventing direct contact and potential shorts while allowing the gate structure to remain sealed and protected.
2Reliability
If a protective layer is added over the gate structure during frontside processing, then gate structure protection is achieved, but process complexity increases
Solution Approach 1:
The formation of the backside dielectric cap is merged with existing frontside processing steps. The cap is formed as part of the frontside fabrication sequence, combining protection functionality with standard process flows rather than adding separate, dedicated protection steps.
Solution Approach 2:
The backside dielectric cap serves multiple functions: it protects the gate structure from contact shorts, prevents hydroxyl group diffusion that would cause threshold voltage shifts, and provides a sealing barrier. This multi-functionality reduces the need for multiple separate protective measures.
Data Source
AI summary
A semiconductor structure is provided that includes a backside dielectric cap which seals the gate structure thus preventing gate structure exposure during backside processing. The presence of the backside dielectric cap helps to mitigate gate to direct backside source/drain contact shorts. The backside dielectric cap is formed during frontside processing.